Pulverizer

ABSTRACT

APPARATUS IS PROVIDED FOR PULVERIZING RAW COAL FEED STOCK INTO COMMINUTED PARTICLES WHICH CAN BE CONVEYED TO THE COMBUSTION CHAMBER OF A FURNANCE. AN ABRASIVE OFERLAY IS DEPOSITED ON THE THRUST RING OF THE PULVERIZER TO PREVENT SKIDDING THE ROLLERS.

Sept. 20, 1971 PULVERIZER Filed Oct. 21, 1969 I, III. I k ,2 l 22 IIV' "I m -H I M. 1 M a y.

C. J. ROMANOWSKI ETAL 2 Sheets-$heet 1 INVI'IN'IURS. CHESTER J. ROMANOWSKI GUY A. LeCLAIR BY HARRY H. PRATT MARVIN A. NAIGUR AT TORNE Y Sept. 20, 1971 c, RQMANQWSKI ETAL 3,606,179

PULVERIZER Filed Oct. 21, 1959 2 Sheets-Sheet 2 INVIiN'I ()KSI CHESTER J. ROMANOWSKI MARVIN A. NAIGUR ATTQRNE Y United States Patent 3,606,179 PULVERIZER Chester J. Romanowski, Carteret, N.J., Guy A. Leclair,

Mountaintop, Pa., and Harry H. Pratt, West Orange,

N.J.,NasIsign0rs to Foster Wheeler Corporation, Livingston,

Filed Oct. 21, 1969, Ser. No. 868,006 Int. Cl. B02c /00; F16h 13/00 US. Cl. 241103 8 Claims ABSTRACT OF THE DISCLOSURE Apparatus is provided for pulverizing raw coal feed stock into comminuted particles which can be conveyed to the combustion chamber of a furnace. An abrasive overlay is deposited on the thrust ring of the pulverizer to prevent skidding of the rollers.

BACKGROUND OF THE INVENTION In connection with the operation of relatively large coal fired furnaces which are used in vapor generating systems in the utility industry for production of electricity, it is necessary to supply finely powdered coal to the combustion chamber of the furnace. The raw coal feed stock is usually reduced to comminuted particles in a pulverizer apparatus which generally consists of a rotating grinding table on which there is formed a grinding surface, and relatively heavy rollers are journaled within the apparatus and maintained in contact with the grinding surface by a thrust ring.

There has recently developed a major problem in connection with the pulverizing of coal feed stocks containing particles which cannot easily be pulverized by the apparatus, such as iron pyrite and the like. These rela tively hard constituents are more commonly found in many types of coal which are being mined today. The hard particles often prevent the pulverizing apparatus from functioning efficiently, in that skidding action is translated to the rollers along the grinding table. -In accordance with the present invention, the skidding of the rollers has been eliminated by providing positive engagement between the rollers and the thrust ring. This is achieved by depositing an overlay of tungsten carbide particles in a molten pool of metal along the lower periphery of the thrust ring. Thus, when a hard particle be comes lodged between the grinding surface of a roller and the rotating bed, the positive engagement of the abrasive overlay with the rollers will prevent the rollers from skidding.

SUMMARY" OF THE INVENTION In accordance with an illustrative embodiment demon strating features and advantages of the present invention, there is provided an apparatus for pulverizing material into comminuted particles including a housing and a table having a grinding surface mounted in the housing for rotation. Means are provided for rotating the table and for introducing the material into the housing in contact with the grinding surface. A plurality of rollers each having a peripheral grinding face are maintained in contact with the grinding surface. A thrust ring is mounted in contact with the rollers, and the thrust ring is coated with an abrasive overlay for contacting the rollers such that the rollers are prevented from skidding along the table.

BRIEF DESCRIPTION OF THE DRAWINGS The above brief description as well as further Objects, features, and advantages of the present invention will be more fully appreciated by reference to the following detailed description of a presently preferred but nonethe- 3,606,179 Patented Sept. 20, 1971 less illustrative embodiment in accordance with the present invention, when taken in connection with the accompanying drawings wherein:

FIG. 1 is a front sectional view of a portion of a pulverizing apparatus embodying features of the present invention;

FIG. 2 is an enlarged sectional view of part of the thrust ring and a roller of FIG. 1, showing the abrasive overlay in engagement with the rollers;

FIG. 3 is an enlarged bottom plan view of the thrust ring and rollers shown removed from the pulverizing apparatus in FIG. 1 in order to more clearly show the contact between the thrust ring and rollers; and

FIG. 4 is a partial elevational view of the thrust ring shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to -FIG. 1, a pulverizing apparatus is shown which is generally designated by the reference numeral 10. The pulverizing apparatus 10 includes a steel housing 12 which is mounted at ground level for enclosing a support 14 on which there is rotatably mounted a grinding unit 16. Raw coal feed stock is introduced into the housing 12 through a conduit system 18 which is generally located above the grinding unit 16.

The grinding unit 16' includes a table 20 formed with an annular groove 22 which defines a grinding surface S. The table 18 is mounted for rotation on the support 14 by means of a rotating hub 24 which is powered by an electric motor which has not been shown in the drawings for the sake of simplicity.

A plurality of spaced apart pulverizing rollers 26, preferably three in number, which have a grinding face F, roll in groove 22. Spacer means that are well known in the art, and which have not been shown in the drawings are disposed between the rollers 26. Each of the rollers 26 is formed with a bearing collar 30 which is formed with an annular groove 32. A thrust ring 34 is mounted in housing 12 above the pulverizing rollers 26, and load is applied by means of compression springs 36. The thrust ring 34 is integrally formed with an annular lip 38 which is configurated in accordance with the outer periphery of annular groove 32 in order to achieve smooth mating contact.

As best shown in FIGS. 2 and 4, annular lip 38 is defined by an inner inclined face 40, a bottom circular face 42, and an outer inclined face '44. The inclined faces 40 and 44 are respectively coated with an inner wearresistant overlay 46 and an outer abrasive overlay 48. The overlays 46 and 48 are obtained by forming a molten metal pool from an oscillating tungsten inert gas welding torch, with the abrasive overlay 48 being formed by depositing tungsten carbide particles in the metal pool. Thus, the inner overlay 46 is made wear-resistant but nonabrasive since sliding must occur between the inner overlay 46 and annular groove 32. It is preferable to use tungsten particles in the range of from 20 to 30 mesh, and the abrasive overlay 48 provides a soft matrix with a tough, resilient, wear-abrasive, and high friction surface.

Accordingly, by referring to FIG. 2 it can be seen that the inner wear-resistant overlay 46 and the outer abrasive overlay 48 are in mating contact along the surface of annular groove 32. In this manner, positive engagement is obtained between the thrust ring 34 and the pulverizing rollers 26, such that skidding between the grinding surface S and grinding face F is reduced.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed Without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

What is claimed is:

1. Apparatus for pulverizjng material into comminuted particles comprising a housing, a table having a grinding surface mounted in said housing for rotation, means for rotating said table, means for introducing said material into said housing in contact with said grinding surface, a plurality of rollers each having a peripheral grinding face maintained to contact said grinding surface, a thrust ring mounted in contact with said rollers and said thrust ring coated with an abrasive overlay for contacting said rollers such that said rollers are prevented from skidding along said thrust ring.

2. Apparatus according to claim 1 in which said abrasive overlay is formed from tungsten carbide particles deposited in a molten metal pool.

3. Apparatus according to claim 1, in, which said rollers are integrally formed with an outer circular hearing collar and said abrasive overlay contacts said rollers along the circumference of said collar.

4. Apparatus according to claim 3, in which an annular lip is integrally formed on said thrust ring and said bearing collar is formed with an annular groove capable of achieving mating contact with said annular lip.

5. Apparatus according to claim 4, in which said annular lip is defined by an inner inclined face and an outer inclined face.

6. Apparatus according to claim 5, in which said abrasive overlay is formed on said outer inclined face.

7. Apparatus according to claim 6, in which said abrasive overlay is formed from tungsten carbide particles deposited in a molten metal pool.

8. Apparatus according to claim 5 in which a Wearresistant overlay is formed on said inner inclined face.

References Cited UNITED STATES PATENTS 4/1938 :McErlean 24ll03X 1/1968 Barton 24l103X U.S. Cl. X.R. 74-l94; 24l300 

